Interactions between invertebrate and mycotoxin-producing fungi
by Yang Xu
Date of Examination:2018-08-07
Date of issue:2018-12-12
Advisor:Prof. Dr. Petr Karlovsky
Referee:Prof. Dr. Stefan Vidal
Referee:PD Dr. Franz Hadacek
Persistent Address:
http://dx.doi.org/10.53846/goediss-7192
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Abstract
English
Interactions between fungi and invertebrates nearly occur in every ecosystem. Grazing affects fungal biomass density and is species-dependent. However, how invertebrates affect mycotoxin-producing fungi has not been studied yet. In our study, we exposed three well-known mycotoxin-producing Fusarium strains (F. graminearum, F. culmorum and F. verticillioides), two Aspergillus strains (A. nidulans and A. ochraceus) and one Penicillium strain (P. viridicatum) to intense grazing by Folsomia candida and determined fungal biomass gravimetrically and by quantitative real-time PCR. Our results indicated that only A. nidulans and F. verticillioides were consumed in larger amounts by the collembolan. The mycelial biomass of A. ochraceus even increased after grazing commenced. Our results suggest that collembolan grazing caused variable effects on the mycelial growth of mycotoxin-producing fungal strains but no uniform reduction.Collembolans are selective feeders. Their food preference contributes to shaping of fungal community composition in various ecosystems. Previous experiments showed that F. candida grazing caused different fungal biomass loss effect on F. verticillioides and F. graminearum. This is intriguing regarding to their biological similarity. In this study, we explored the food preference of the springtail Folsomia candida between F. verticillioides and F. graminearum in terms of various aspects: (1) which spies is more attractive, F. verticillioides or F. graminearum; (2) how attractive are the mycotoxin-deficient F. graminearum strains, ∆DON (lacks deoxynivalenol), ∆ZEN (lacks zearalenone), ∆AUR (lacks aureofusarin); and (3) to which extent does mixing of cultures affect collembolan grazing. Collembolan activity was determined by eye observation and real time PCR of DNA mycelium extracts. In our assays, F. candida prefers F. verticillioides and avoids F. graminearum. However, the one F. graminearum mutant is attractive to F. candida over F. verticillioides. In addition, springtails prefer mixtures of two fungal strains to a single strain. Even the avoided F. graminearum is consumed in higher amounts, when another fungal strain is present. The obtained provide support for the hypothesis that fungal secondary metabolitecan contribute to the avoidance of a specific fungal species by a collembolan grazer. Additionally, a fungal strain that produces a feeding deterrent compound can be consumed in higher amounts in a mixed community than a sole food source.
Keywords: Mycotoxin-producing fungi, invertebrate, fungal defence.
